Air-cooled electric terminals for an incinerator

ABSTRACT

An electrically heated incinerator is disclosed wherein an electrically resistive heating element is disposed in a separate heater compartment adjacent a combustion chamber. Electric power for the heating element is provided by a pair of electric terminals extending from the heatear compartment to an outside portion of the incinerator. In order to cool the electric terminals and remove or consume deposits formed on the terminals which may short the electric current to ground, a cool, oxygenrich airflow is provided for the terminals. This airflow is obtained by tapping a small portion of secondary airflow within a passageway and directing it through appropriate ductwork against the terminals and into the heater compartment.

[ June 17, 1975 United States Patent [1 1 Eff [ AlR-COOLED ELECTRIC TERMINALS FOR AN INCINERATOR Primary Examiner-Kenneth W. Sprague [75] Inventor: Christian A. Eff, Louisville, Ky.

General Electric Company,

[57] ABSTRACT An electrically heated incinerator is disclosed wherein an electrically resistive heating element is disposed in a separate heater compartment adjacent a combustion n 9 Pu l m2 m u r o P LA e n .m d S e s H A F 1 3 2 7 2 l .l

[21] Appll 51 4 0373 chamber. Electric power for the heating element is provided by a pair of electric terminals extending from the heatear compartment to an outside portion of the incinerator. In order to cool the electric terminals and remove or consume deposits formed on the terminals which may short the electric current to ground, a cool,

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oxygen-rich airflow is provided for the terminals. This [56] References Clted airflow is obtained by tapping a small portion of sec- UNITED STATES PATENTS ondary airflow within a passageway and directing it through appropriate ductwork against the terminals and into the heater compartment.

llO/S E 1 10/ A 2 Claims, 4 Drawing Figures Raucher....

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AIR-COOLED ELECTRIC TERMINALS FOR AN INCINERATOR BACKGROUND OF THE INVENTION l. Field of the Invention The invention relates to electrically heated incinerators and, more particularly, to means for cooling the terminals of electrical heating elements in an electrically heated incinerator.

2. Description of the Prior Art In the electrically heated incinerator art, it is well known to provide a combustion chamber wherein combustible materials are incinerated and a separate chamber, known as a main heater compartment, wherein electrically resistive heating elements are disposed. Air is heated by the heating elements and conducted to the combustion chamber where, after a period of time has passed in which the air has been heated sufficiently, the combustible materials are incinerated. At the beginning of the incineration cycle, ambient air is precluded from entering the combustion chamber to control the combustion process and vaporize the moisture and other volatiles in the combustible materials.

Although the temperature within the combustion chamber is generally around 800F, the temperature in the main heater compartment may exceed I500F. The high temperatures in the main heater compartment are very destructive of electric terminals contained therein. Consequently, premature failure of the electric terminals is not uncommon.

A second problem encountered in prior art devices is that air circulated from the combustion chamber to the main heater compartment is rich in unburned carbon, soot, and partially burned hydrocarbons. There fore, an electrically conductive coating may be deposited on exposed surfaces within the main heater compartment. Such a coating may under certain circumstances result in shorting of the electric power supply to ground, with a resultant loss in heating capability.

Accordingly, it is an object of the present invention to provide electric terminals for an electrically heated incinerator, which terminals are maintained at a temperature low enough to prevent premature failure.

It is another object of the invention to prevent the shorting to ground of the electrical power supplied to electrical heating elements in the main heater compartment of an incinerator.

It is a further object of the invention to prevent undesirable deposits from forming on electric terminals and components associated therewith disposed within the main heater compartment of an electrically heated incinerator.

SUMMARY OF THE INVENTION In carrying out the invention, in one form thereof, an electrically heated incinerator includes a separate heater compartment within which is disposed an electrically resistive heating element. Electric current for the heating element is provided by a pair of electric terminals extending from the heater compartment to an outer portion of the incinerator. In order to cool the terminals and remove or consume any deposits formed on the terminals and components associated therewith, a cool, oxygen-rich airflow is provided for the terminals. This airflow is obtained by tapping a small portion of the airflow within a passageway and directing it through an appropriate ductwork against the terminals and into the heater compartment.

DESCRIPTION OF THE DRAWING FIG. I is a cross-sectional view of an incinerator according to the invention showing the combustion chamber and certain ductwork associated therewith and a loading door and access cover in an open position.

FIG. 2 is a cross-sectional view of an incinerator according to the invention similar to FIG. I, but also showing a main heater compartment having heater elements and electric terminals disposed therein, an afterburner compartment, and the loading door and access cover in a closed position.

FIG. 3 is a cross-sectional view taken on line 33 of FIG. 2, showing a pair of electric terminals and their associated components.

FIG. 4 is a block flow diagram showing the main ele' ments of the incinerating process, as well as the various flow patterns for primary and secondary air streams.

DESCRIPTION OF THE PREFERRED EMBODIMENT An incinerator 10 is shown in FIG. I. Incinerator 10 includes an outer incinerator housing I2 of sheet metal, box-like construction that defines the outer limits of the incinerator and forms a supporting structure for the operational components of the incinerator system. The present invention deals with cooling of electric terminals in the heating means of such an incinerator. The incinerator in which the present invention is shown is described more fully in two prior patents of the present inventor, US. Pat. No. 3,742,874, Solid Waste Incinerator, and US. Pat. No. 3,788,243, "Domestic Solid Waste Incinerator." Certain of the drawings of the prior patents are employed to illustrate the present in vention.

It will be appreciated that an incinerator is a hightemperature device reaching temperatures above l500F in some areas, and that thermal insulting means must be provided within the housing I2 to ensure that the external surface temperatures of the incinerator are kept low. An air space II is formed interiorly each outer wall of the housing 12 by means of an insulation wall 14 spaced apart from housing 12 and which insulation wall has associated therewith a layer of thermal insulation 13. Air space II permits the circulation of cooling air for lowering the external temperature of housing 12.

As shown in FIG. 1, the incinerator includes a combustion chamber 20 formed by an inner liner 22 and a removable, top access cover 24 for loading the com bustion chamber with combustible material through a front-loading door 16. The inner liner 22 has a forwardly inclined, semi-cylindrical front wall 26 with a generally perpendicular, imperforate bottom wall 28, a generally vertical rear wall 33, and a top wall 36 having a downwardly inclined front portion 37. Access cover 24 cooperates with an opening 38 in the downwardly inclined front portion 37. Moreover, access cover 24 is provided with a sealing gasket 39 which is adapted to be compressed tightly against the peripheral flange of opening 38 for rendering the combustion chamber 20 generally air-tight and precluding the escape of heated gases, smoke, odors, vapors, and the like. A suitable linkage 4i connects loading door I6 with access cover 4 whereby for each movement of the loading door iere is a similar movement of the access cover so that is not necessary to handle both the door 16 and the over 24 separately as this would be very inconvenient. sually the combustible materials would be held in one and and the loading door 16 would be opened with the ther hand and the cover 24 would move simultaeously in order that the combustible materials could e inserted through the opening 38 and dropped into ombustion chamber 20.

Turning attention to the gas flow block diagram of 1G. 4. a brief outline of the overall incinerating system 'ill be given. Primary air enters the combustion chamer 20 through an open damper 105 after the chamber :mperature rises above about 350F. This primary air asses down through duct 106 and then passes through ie waste load and is drawn into a first scroll wheel 107 iat is located adjacent the top wall 36 of the combuson chamber. This first scroll wheel 107 has a split disharge with a first downwardly inclined discharge back no the combustion chamber and a second generally orizontal discharge duct 64 which leads out of the ombustion chamber and discharges into a fly ash sepaator 66 in the form of a series of four cyclone separa Jl'S for separating the fly ash from the flue gases.

The gas passes from the fly ash separator 66 to a preeater unit 108 for raising the temperature of the gas o a maximum of about 1,lOOF before the gas is delivred to the main heater compartment 46.

From the main heater compartment 46, part of the as is returned to the combustion chamber 20 and reirculated. The remaining amount of the gas is delivred to an afterburner unit 74 which is located beneath he main heater compartment 46.

Since there is a reduced amount of oxygen dischargng from the main heater compartment 46, a supply of econdary air is provided for the afterburner 74 so as o oxidize the combustibles that might still be entrained n the flue gases. This secondary air is brought into the ncinerator housing by means ofa second blower wheel .10. The function of the secondary air is to cool the vindings of the blower motor 62 as well as to cool [own the walls of the combustion chamber 20, and iirally to supply oxygen to the afterburner 74 for oxidizng the combustibles in the flue gases. Part of this sec- )ndary air stream is directed through duct 88 over the nner ends of the electrical terminals 50.

A third blower wheel 11] is part of an exhaust system vhich is arranged downstream of the afterburner for 'eturning the flue gases to the outside atmosphere.

Now going back to the design details of FIG. 2, it is )OSSiblE to locate the incinerator heating means so that he heating means are in direct contact with the com- )ustible materials. The heating means could be located vithin the combustion chamber 20 adjacent the top of nner liner 22 and away from opening 38. However. it ias been deemed preferable to locate the heating neans in the form of an open resistance heating elenent 44 in a main heater compartment 46 which is p iiIlUl'lflCl at the front of the incinerator housing generilly beneath the forwardly inclined. semicylindrical ront wall 26 of inner liner 22. Resistance heating elenent 44 is of wire form, such as nickel-chromium wire, hat is supported on a series of ceramic insulators or spools 48 in such a way that a plurality of turns are wound on one spool and the wire is then joined to the adjacent spool 48 and again a plurality of turns are wound on that spool before leading the wire 44 to the next spool. As shown in FIG. 2, there are five insulator spools supporting the nichrome wire, although the number of insulator spools is a matter of choice.

Main heater compartment 46 also has an inner wall 54, a bottom wall 55, and an inclined, semicylindrical rear wall 57 which is spaced slightl; t2 inclined, semicylindrical front wall 26 of inner liner 22 of the combustion chamber to form a cooling air channel 58 for handling a flow of secondary room ambient air for cooling the walls of inner liner 22. A layer of insulation 59 covers the inner surface of the walls forming main heater compartment 46.

A blower 60 is located in the upper portion of the incinerator housing, which blower is powered by an electric motor 62. Blower 60 is mounted in a split scroll (not shown) which has two discharge openings: a downwardly inclined discharge opening (not shown) within the combustion chamber 20 and a generally horizontal discharge duct 64 which leads out to an opening in the side wall of the inner liner 22 of combustion chamber 20 and discharges into a fly ash separator in the form of a series of four cyclone separators. The first cyclone separator 66 is seen in FIG. 1. The downwardly inclined discharge opening (that is not illustrated) directs a blast of air into the combustion chamber at a high velocity so that the air is able to reach the many isolated air pockets within the combustible material and to support the combustion thereof Also, there is an airstream from the combustion chamber 20 drawn into an air inlet opening (not shown) in the side of the scroll of the blower 60. One part of this airstream is divided out to return to the combustion chamber through the downwardly inclined discharge opening and the remaining part of the airstream is directed through the horizontal duct 64 to pass into the first cyclone separator 66.

It is important to separate fly ash from the flue gas as it exits from the combustion chamber 20 through the discharge duct 64. Rather than provide a single fly ash separator. it has been elected to adopt a more efficient system of a grouping of four cyclone separators each of generally standard design characteristics and each with its own removable ask collector at the bottom, such as the quart jar 68 shown in FIG. 1. A front access door 69 having a handle 70 is provided near the lower portion of the cyclone separators for periodically removing and emptying the ash collectors.

After passing through the flow ash separator, the airstream enters a preheater (not shown) which is vertically mounted just behind the fly ash separator. The purpose of the preheater is to raise the temperature of the gas to a maximum of about 1 l0OF before the gas is delivered to the main heater compartment 46 where the gas is heated further to about 1500F so that most of the smoke, odors. and vapors are consumed. After being heated in the preheater, the gas exits into the main heater compartment 46 through an opening 71, as shown in FIG. 1.

From the main heater compartment 46, the gas returns to the combustion chamber 20 through upper openings 72 where the heated gas is first drawn into the blower 60 and is separated by the split scroll so that part of the gas is blasted into the combustion chamber through the downwardly inclined discharge opening and the remainder of the gas is exhausted from the combustion chamber through the discharge duct 64 to the fly ash separator. Thus, it will be understood that hot gases are recirculated within the combustion chamber 20 through the blower 60 and the downwardly inclined discharge opening, while there is a second recirculation system for the combustion chamber comprising the discharge duct 64, the fly ash separator, the preheater, and the main heater compartment 46. The air flowing back through the combustion chamber continues this recycling action for removing as much of the fly ash from the flue gas as is possible, for consuming the smoke, odors, vapors, and volatiles entrained therein, and for reheating the air for the ignition of the combustible materials. It will also be understood that during the initial phase of the combustion cycle most of the oxygen present in the air and gas existing within the combustion chamber is consumed by the ignition of the combustible materials and is not replenished during the recycling through the fly ash separator, preheater, and main heater compartment and back to the combustion chamber. This oxygen-starved condition serves to control the combustion process and prevent backfires. As the volatiles within the combustible materials are driven off, so-called primary air is directed to the combustion chamber only after the temperature within the combustion chamber reaches about 800F in order to support combustion of the combustible materil for the remainder of the incineration cycle. The primary air enters the combustion chamber through the damper 105 and duct 106 in the back wall 33 of the combustion chamber near the bottom thereof. Referring to FIG. 2, an afterburner 74 is dispose downstream of the main heater compartment 46 so that not all of the gas passing through the main heater compartment 46 is returned to the combustion chamber 20. A small amount of the gas is passed to the afterburner 74 by way of a vertical duct (not shown) which empties into the afterburner 74. A layer of insulation 76 covers the walls forming the afterburner chamber 74. Since there is a reduced amount of oxygen in the gases discharging from the main heater compartment 46, a supply of secondary air is provided for afterburner 74 so that any combustibles that might still remain in the flue gases are oxidized. This secondary air is brought into the incinerator housing by means of a second blower 78, the periphery of which is shown in cross-section in FIGS. 1 and 2. Leading from a scroll around second blower 78 is an inclined exhaust duct 80 which enters the air channel 58 shown in FIG. 2 through an opening 82 in the wall 57 that parallels the front wall 26 of inner liner 22. The secondary air is in contact with the semicylindrical front wall 26 of inner liner 22 for cooling the walls of the combustion chamber as well as for preheating the secondary air before it enters afterburner 74 through a plurality of lower openings 84 shown in FIG. 2. After passing through air channel 58, the secondary air is at a temperature of about 300-600F.

Referring to FIG. 2, a secondary air duct 86 at the back of the incinerator having an intake opening 85 near the floor and having an upper opening adjacent motor 62 provides a passage for room ambient air to the motor for cooling the windings thereof before being drawn into second blower 78. Thus, the function of the secondary air is to cool the windings of motor 62 as well as to cool the walls of the combustion chamber 20 by passing secondary air through air channel 58. The secondary air then supplies oxygen to afterburner 74 for oxidizing the combustibles in the flue gas after it exits from the main heater compartment 46.

A further function of the secondary air is part of the invention. Most of the secondary air passing through air channel 58 enters afterburner 74 through top openings 84. However, a portion of the secondary air bypasses openings 84 and is conducted through a pair of openings 87 formed in bottom wall 55 of main heater compartment 46. The secondary air entering openings 87 is conducted upwardly through ducts 88 to electric terminals 50.

Referring to FIGS. 2 and 3, each terminal is comprised of a metal clamp 90 fastened about outwardly extending flanges 92 of duct 88. The clamps are held in place by bolted fasteners 94 which engage clamps 90 near the top thereof. Disposed within each metal clamp is a longitudinally extending, triangle-shaped ceramic insulator 96. Centrally disposed within each ceramic insulator 96 is a lead-in member 97 comprised of .5 inch diameter cold-rolled steel. in order to prevent electric current from shorting to ground due to the build-up of carbon deposits on lead-in member 97, lead-in member 97 includes a reduced-diameter end portion 98 at the inner end thereof, as seen in FIG. 2, which end portion is spaced from ceramic insulator 96. Each ceramic insulator 96 includes a hole 99 formed in a lower, inner portion thereof. Hole 99 is disposed immediately above duct 88 in order that secondary air entering duct 88 may be conducted through the lower portion of ceramic insulator 96 and past end portion 98 of lead-in member 97. Main heater element 44 is connected to end portion 98 of lead-in member 97 while an electric power lead 100 is connected to the outer end of lead-in member 97 through an electric terminal strip 102.

In order to connect electric power lead 100 to main heater element 44, it is necessary that terminals 50 extend from the outside of the incinerator into main heater compartment 46. Thus, it is seen that terminals 50 comprising clamps 90, ceramic insulators 96, and lead-in members 97 extend through insulation wall 14, inner wall 54, and insulation layer 59. Electric power lead 100 may be conducted through outer incinerator housing 12 at any convenient location.

OPERATION The operation of the incinerator with respect to the invention is as follows. After combustible materials are placed in combustion chamber 20, loading door 16 and access cover 24 are closed and the incineration cycle started. Electric current is conducted through electric power leads 100, electric terminal strips 102, and leadin members 97 to heating element 44 disposed within main heater compartment 46. Heated air from main heater compartment 46 is conducted to combustion chamber 20 where incineration of the combustible materials is commenced. The recirculating system sends a portion of the air extracted from combustion chamber 20 through the fly ash separator 66 and the preheater 108 before directing the air back to main heater compartment 46. In order to consume moisture and volatiles in the combustible materials, no air is admitted to combustion chamber 20 in the initial stages of the incineration cycle. As a consequence, main heater compartment 46 is in an oxygen-starved condition resulting in an atmosphere rich in unburned carbon, soot, and partially burned hydrocarbons. Thus, an electrically conductive coating may be deposited on lead-in members 97, ceramic insulators 96, and the rest of the components of the electric terminals, resulting in a shorting to ground of electric current.

In order to remove or consume any particles deposited on the components comprising terminals 50, an oxygen-rich airflow is provided for the terminals. A portion of the heated gas exhausted from main heater compartment 46 is directed to an afterburner 74. A secondary airflow is provided to increase the amount of oxygen in afterburner 74. A small amount of this cooler, oxygen-rich secondary airflow is conducted through openings 87 in bottom wall 55 through ducts 88 past those elements comprising electric terminals 50 in order to remove or consume particles deposited thereon.

It will be recognized by those skilled in the art that openings 87, ducts 88, and holes 99 should be sized so as not to upset the intended airflow balance in the main heater compartment. If these elements are properly sized. the electric terminals are maintained at a temperature low enough to prevent premature failure; shorting to ground of the electrical heating elements is eliminated; and deposits either do not form on the heater terminals or are removed or consumed shortly after deposition. An incinerator employing the air-cooled electric terminals ofthe invention has been built and tested. Test results from over 100 experiments indicate that the invention accomplishes all the desired results previously mentioned.

Although a specific embodiment of the invention has been described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention. It is therefore intended in the appended claims to cover all such changes and modifications that fall within the true spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. In an incinerator having a combustion chamber; a heater compartment external said combustion chamber; electrical heating means disposed in said heater compartment for causing incineration of combustibles deposited within said combustion chamber; an electric terminal extending from said heater compartment for connecting said electrical heating means to an electrical source external said incinerator for powering said heating means, said terminal further comprising an elongated clamp extending from said heater compartment to an outer portion of said incinerator, a ceramic insulator disposed within said elongated clamp, and a lead-in member disposed within said ceramic insulator; and a passageway intermediate said combustion chamber and said heater compartment for the passage of air, the improvement comprising:

ducting means connecting said heater compartment and said passageway, said ducting means being disposed adjacent said clamp and ceramic insulator of said terminal to direct air flowing from said passageway against said lead-in member and into said heater compartment.

2. The apparatus of claim 1 wherein said lead-in member includes a reduced-diameter end portion at the inner end thereof, said end portion being spaced from said ceramic insulator. 

1. In an incinerator having a combustion chamber; a heater compartment external said combustion chamber; electrical heating means disposed in said heater compartment for causing incineration of combustibles deposited within said combustion chamber; an electric terminal extending from said heater compartment for connecting said electrical heating means to an electrical source external said incinErator for powering said heating means, said terminal further comprising an elongated clamp extending from said heater compartment to an outer portion of said incinerator, a ceramic insulator disposed within said elongated clamp, and a lead-in member disposed within said ceramic insulator; and a passageway intermediate said combustion chamber and said heater compartment for the passage of air, the improvement comprising: ducting means connecting said heater compartment and said passageway, said ducting means being disposed adjacent said clamp and ceramic insulator of said terminal to direct air flowing from said passageway against said lead-in member and into said heater compartment.
 2. The apparatus of claim 1 wherein said lead-in member includes a reduced-diameter end portion at the inner end thereof, said end portion being spaced from said ceramic insulator. 